Nonoverhaul apparatus for hydraulic systems



H. W. LINK NON-OVERHAUL APPARATUS FOR HYDRAULIC SYSTEMS Filed June 12, 1943- I 2 Sheets-Sheet 1 INVENTOR Hazy/1511M ATTORNEY 4, 19., H. w. LINK 2,44,961 NON-OVERHAUL APPARATUS FOR HYDRAULIC SYSTEMS Filed June 12, 1943 2 Sheets-Sheet 2 INVENTOR Patented May 4, 1948 NONOVERHAUL APPARATUS FOR HYDRAULIC SYSTEMS Barry W. Link, Mei-ion, Pa., assignor to The Baldwin Locomotive Works, a corporation of Pennsylvania Application June 12, 1942, Serial No. 490,101

momma. (01. 60-53) This invention relates generally to cranes and more particularly to non-overhaul apparatus whereby a lowering load on the crane cable cannot run away.

In lowering a load by a crane it is desirable to keep the speed below a predetermined value not only-from the standpoint of safety and reduction.

of maintenance of the equipment, but also for proper handling of the cargo. This problem can be particularly critical in the handling of equipment, such as seaplanes, during transfer of the same from the deck of a ship to the water, although my invention is applicable to other fields where similar problems are present.

In the particular crane system disclosed herein a cable drum is operated by a reversible hydraulic motor driven from a reversible variable displacement pump of the Hole-Shaw or equivalent type. Hence during lowering of the load the motor tends to act as a pump to circulate fluid back through the pump system. Such a hydraulic system has not been conducive to maintaining a, proper non-overhaul speed even though the variable displacement pump is adjusted to a position that would ordinarily effect a proper lowering speed.

It is' an object of my invention to provide an valve which is controlled by the valve means of Fig. 2.

In the specific embodiment of the invention disclosed herein for purposes of illustration 1 have diagrammatically shown in Fig. 1 a crane i of any suitable type having a cable 2 adapted to be wound on or unwound from a drum 3. This drum is driven through any suitable gearing or connections from a hydraulic motor 4 of any usual and well-known type such as-having pistons and cylinders, vanes, gears, etc., for which operating improved non-overhaul control for a hydraulically operated crane system.

Another object is to provide an improved hydraulic type non-overhaul apparatus for a hydraulically operated crane system in which the non-overhaul device is rendered operative automatically when a. lowering crane operation is initiated.

- A further object is to provide an improved nonoverhaul apparatus that is relatively simple and economical in construction, operation and main tenance and has a high degree of sensitivity and responsiveness without interfering with the efficiency of the hydraulic operation during raising of a load.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 diagrammatically illustrates a crane whose cable is hydraulically operated and embodies my improved non-overhaul control;

Fig. 2.15 a sectional view of the pull and back pressure regulating means of my improved control apparatus together with a fragmentary portion of the operating cam; and

Fig. 3 is a sectional view or a main pump line tioned. a. lowering load tends to rotate the motor 24 of the valve passage.

opening piston area 25 exposed to the pump end fluid is supplied from a suitable hydraulic pump 5. This pump is preferably of the reversible variable displacement piston type such as'Hele-Shaw or other equivalent type. Inasmuch as the foregoing types of pump and motor are well-known further description need not be given. It will sufiice to state that pump 5 may be shifted from forward to reverse or to neutral by an axially movable control stem t which may be manually adjusted by a cam I through a 'handwheel 8. As shown in Fig. 2 the cam has a neutral position 9, alowering cam surface l0 and a hoisting cam surface It whereby when the hoisting cam H is rotated the pump discharges fluid through a pipe It to motor it while the, discharge from motor 6 returns to the pump by a pipe l5.- Conversely, when lowering cam I0 is operative the pump draws fluid from the motor through pipe Id and allows fluid to return to the motor through pipe l5. Notwithstanding that the lowering cam surface In is designed for a lowering speed less than the hoisting speed still, as previously men- 4 with an overhaul speed that is greater than desired or sometimes safe. To prevent the forego ing overhaul speed, I have provided my improved control apparatus shown in Figs. 2 and 3. A valve l-l disposed in the line It leading from the pump to the motor is provided with a fluid sup-' ply passage adapted to be controlled by an' end seating valve l8 which has a piston l9 operating in a cylinder 20. A spring 2i for normally biasing the valve to its closed position is seated against an upper valve stop 22. A port 23 allows a restricted .flow to cylinder 20 from the motor end The piston B! has an 26 of the valve passage whereby during supply of pump fluid to the motor for raising a load, the pump pressure engages piston area 25 to open valve l8 and so maintain the same thereby allowing free unimpeded flow of fluid to the hydraulic motor. During lowering of a load it is desirable not to allow fluid to flow from the motor to the pump, 1. e. irom 24 to 26, in excess a predetermined rate thereby to control the speed 0! lowering. 0n the other hand, during raising of the load it is desired to allow unimpeded flow from the pump to the motor through the same fluid passageway 24, 26. To accomplish the function of unimpeded flow past valve IS the piston chamber 20 is freely exhausted through an outlet 28 by a pilot valve 29, this pilot valve being moved downwardly by cam II when handwheel 8 adjusts pump to its hoisting position. The pilot valve is of the two spool type with an intermediate annular space for connecting a passage 30 with exhaust port 28 and is normally biased upwardly by a spring 3| to its closed position. The pilot valve also may be moved manually by a lever 32 to its exhaust position. Thus it is seen that by connecting passage 30 with cylinder fluid can be exhausted from the latter so that pressure in passage 26 will act on piston area to open the valve l8 and so maintain it. However, when pump 5 is adjusted to its lowering position by handwheel 8, then cam surf-ace i0 is adapted to permit pilot valve 29 to be moved by spring 3| to its closed position whereupon when the generated discharge pressure from the motor during reverse operation reaches a predetermined value in cylinderchamber 20 a relief valve 33 will allow throttled flow from the chamber and thence to passage 34 to outlet 28. The relief valve 33 is held by a spring 35 whose tension can be adjusted by a suitable threaded rod 35. Inasmuch as the valve 33 will maintain a predetermined pressure in cylinder chamber 20, it is seen that valve l8 will open only to whatever pressure is desired in motor passage 24 thereby to prevent excessive reverse speed of the motor and accordinglycontrol the rate of lowering.

Thus it is seen that the piston area 25 of fluid control valve 18 functions to exert an opening force on the valve in either direction of fluid flow through the main valve passage while the port 23 supplies fluid from this passage to the closing end of the valve piston I9 whereby complete opening of the valve during a. lifting operation, as well as partial opening of the valve during a lowering operation, can both be effectively controlled by the single outlet connection 30 leading to cylinder 20. This passage 30 is then eflectively automatically controlled by the relatively simple cam Ill, ll whose operation is functionally related to that of the direction of pump rotation. The single pilot valve 28 is adapted to eflect either complete opening or the valve l8 during hoisting or to eflect partial opening thereof during lowering.

From the foregoing disclosure, it is seen that I have provided an extremely simple, sensitive and responsive non-overhaul apparatus that is adapted to control the rate of reverse flow from the hydraulic motor so as to prevent an overhaul speed and yet allow free flow to the motor during the hoisting operation. There is no need for braking equipment or other mechanical or hydraulic energy absorbing arrangements thereby reducing maintenance to a minimum as well as rendering the control thoroughly dependable and safe particularly in inexperienced hands.

It will of course be understood that various changes in details 01 construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. A non-overhaul apparatus for a hoisting and lowering system operated by a hydraulic motor comprising, in combination, a hydraulic nonoverhaul valve for controlling the rate of flow of hydraulic fluid from said motor during a lowering operation thereby to determine the lowering speed, means for initiating the raising and lowering operations of said system, and means, rendered operative in accordance with the initiation of the lowering operation, for hydraulically controlling said valve by hydraulic fluid flowing from said motor whereby overhaul of the system may be prevented.

2. A non-overhaul apparatus for a system which is operated to move in one direction by hydraulic power and which is operated in the opposite direction by a force external to the system comprising, in combination, a hydraulic motor, a passage through which pressure fluid is supplied to the motor for operating the same in one direction, means whereby said motor is adapted to be reversely operated by said external force thereby to cause fluid to flow in the opposite direction through said passage from said motor, non-overhaul valve means controlled by the fluid flowing from said motor and adapted to open a predetermined amount during reverse flow through said passage thereby to determine the rate of reverse movement of said external force, and means for varying the extent of predetermined opening of said valve.

3. A non-overhaul apparatus for a system which is operated to move in one direction by hydraulic power and which is operated in the opposite direction by a force external to the system comprising, in combination, a hydraulic motor, a source of hydraulic pressure fluid, a passage through which said pressure fluid is supplied to the motor for operating the same in one direction, means whereby said motor is adapted to be reversely operated by said external force thereby to cause fluid to flow in the opposite direction through said passage from said motor, a hydraulically operated non-overhaul valve in said passage, and means mechanically actuated by said reverse operating means for controlling said valve to open the same by hydraulic fluid flowing to said motor whereby unimpeded flow of operating fluid to said motor may occur during said hydraulic operation of the motor.

4. A non-overhaul apparatus for a hoisting and lowering system operated by a hydraulic motor to which pressure fluid is supplied through a passage during a hoisting operation and from which fluid is discharged through said passage during a lowering operation under the weight of an oblect being lowered comprising, in combination, a non-overhaul valve disposed in said passage, means for biasing said valve in one direction, pressure fluid operating means for moving said valve in an opposite direction; means for supplying pressure fluid to said latter means, and valve means for controlling the fluid for said fluid operating means so as to open said overhaul valve to provide an unimpeded flow of fluid to the hydraulic motor during a hoisting operation and to partially close said overhaul valve during reverse flow through said passage thereby to control the rate of lowering.

5. A non-overhaul apparatus fora hoisting and lowering system operated by a hydraulic motor to which pressure fluid is supplied through a passage during a hoisting operation and from which fluid is discharged through said passage during a lowering operation under the weight of an object being lowered comprising, in combination, a non-overhaul valve disposed in said passage, said valve having a piston provided with an area continuously exposed to the pressure fluid in said passage to bias the valve in an opening direction, a cylinder for said piston, a restricted port for supplying fluid from said passage to said cylinder thereby to exert a closing force on said piston and valve, a control valve having an exhaust adapted to be connected to said cylinder to allow a predetermined opening of said non-overhaul valve or to interrupt said exhaust connectionwhereupon said non-overhaul valve is closed by an accumulation of pressure in said cylinder, and a back pressure relief valve connected to said cylinder to allow discharge from said cylinder when the pressure of reverse flow in said passage reaches a predetermined value whereby the nonoverhaul valve opens to its said predetermined amount.

6. The combination set forth in claim 4 further characterized by the provision of mechanism for determining the direction of fluid flow through the non-overhaul valve, and means whereby said control valve is operated by said mechanism in accordance with the hoisting or lowering operation of the system.

7. A non-overhaul apparatus for a hoisting and lowering system operated by a hydraulic motor from a reversible fluid pressure pump comprising, in combination, a non-overhaul valve for controlling the rate of flow of fluid from said motor during a lowering operation thereby to determine the lowering speed, means for initiating the raising and lowering operations of said system, and means for hydraulically controlling said valve in accordance with the initiation of the lowering operation thereby to prevent overhaul of the system, said means for initiating'the raising and lowering operations of the system including means for shifting the pump from forward to reverse operation or vice versa, a cam actuated by said shift-v ing means having two cam surfaces one of which is for a raising operation and the other of which is for a lowering operation, and the means for hydraulically controlling the non-overhaul valve including a fluid pressure chamber and piston for controlling the opening and closing of said valve and a pilot valve operated by said camffor controlling the fluid pressure in said chamber, whereby in one position of the pilot valve the pressure fluid in the chamber is discharged to allow full opening of the non-overhaul valve during the rais ing operation and in another position the fluid in the chamber is discharged through a restricted opening to allow partial opening of the non-overhaul valve during the lowering operation thereby to retard reverse flow from the hydraulic motor and accordingly control the rate of descent.

8. A non-overhaul apparatus for a hoisting and lowering system operated by, a-hydraulic motor from a reversible fluid pressure pump comprising, in combination, a non-overhaul valve for controlling the rate of flow of fluid from said motor during a lowering operation thereby, to determine the lowering speed, means for initiating the rais ing and lowering operations of said system, and means for hydraulically controlling said valve in accordance with the initiation of the lowering Operationthereby to prevent overhaul of the system, said means for initiating the raising and lowering operations of the system including means for shifting the,pump from forward to reverse operation or vice versa, a cam actuated by said shitting means having two cam surfaces one or which is for a raising operation and the other of which is for a lowering operation, and the means for hydraulically controlling the non-overhaul valve including a fluid pressure chamber and piston for controlling the opening and closing of said valve and a pilot valve operated by said cam for controlling the fluid pressure in said chamber, whereby in one position of the pilot valve the pressure fluid in the chamber is disof opening of the non-overhaul valve is determined by the setting of the spring.

9. A non-overhaul apparatus for a hoisting and I lowering system operated by a hydraulic motor from a reversible fluid pressure pump comprising, in combination, a non-overhaul valve for controlling the rate of flow of fluid from said motor during a lowering operation thereby to determine the lowering speed, means for initiating the rais-l ing and lowering operations of said system, means for hydraulically controlling said valve in accordance with the initiation of the lowering oper; ation thereby to prevent overhaul of the system, said means for initiating the raising and lowering operations of the system including means for shifting the pump from forward to reverse operation or vice versa, a camactuated by said shifting means having two cam surfaces one of which is for a raising operation and the other of which is for a lowering operation, and the means for hydraulically controlling the non overhaul valve including a fluid pressure chamber and piston for by in one position of the pilot valve the pressurefluid in the chamber is discharged to allow full opening of the non-overhaul valve. during the raising operation and in another position the fluid in the, chamber is discharged through a restricted opening to allow partial opening of the non-overhaul valve during the lowering operation thereby to retard reverse flow from the hydraulic motor and accordingly control the rate of descent, and means whereby said pilot valvemay be manually operated independently of the cam so as to release fluid in the chamber and thereby allow the load to be lowered independently of operating conditions.

10. A non-overhaul apparatus for a system which is operated to move in one direction by hydraulic power and which is operated in the opposite direction by a force external to the system comprising, in combination, a hydraulic motor, a passage through which pressure fluid is supplied to the motor for operating the same in one direction, means whereby said motor is adapted to be reversely operated by said external force thereby to cause fluid to flow in the opposite direction through said passage from said motor, non-overhaul valve means adapted to open a predetermined amount during reverse flow through said passage thereby to determine the rate of reverse movement of eeid external force, and mean: for

varying the extent of predetermined opening or said va1ve,'ea.id means for varying the extent oi predetermined opening oi. the non-overhaul valve comprising a. fluid pressure chamber and an adjustable pressure relief valve connected to said chamber for determining the pressure therein and thereby determine the extent of opening oi the non-overhaul valve. 1

. HARRY W. LINK.

8 REFERENCES mm The following references are of record in the me of this patent:

UNITED STATES PATENTS Number Name Date 1,453,845 Ringle Apr. 24, 1923 2,107,760 MeCormieket 8.1 Feb. 8, 1938 0 2,148,277 Rose Feb. 21, 1939 2,349,284 Kinzelman May 23, 1944 

